Method of extracting silver



UNITED STATES A PATENT OFFICE.

PERCY B. MIDDLETON, 01 NEW YORK, N. Y., ASSIGNOR 01' ONE-HAL! TO JOHN C.

' LALOR, OF NEW'YOBK, NUY.

ME'1HOD OI EXTRACTING- SILVER.

1,372,973. No Drawing.

To all whom it may concern:

Be it known that I, PERCY R. MIDDLETON, a subject of the King of GreatBritain, residing at New York, in the county of New York and State ofNew York, have invented certain new and useful Improvements in Methodsof Extracting Silver, of which the following is a specification.

This invention is a method of extracting silver, together with any goldwhich may be present, from argentiferous ores or residues, in which thesilver exists wholly or in terials.

It is .well known that certain metallic chlorids, including on rous andcupric chlorids and ferric chlorld, have a chlorinating action both uponmetallic silver and silver sulfid. It has heretofore beenuniversallybelieved, so far as I am aware, that these chlorinatingagents act more readily and completelupon metallic silver than uponsilver su fid. I have discovered, however, as the result of considerableexperimentation, that a more com lete chlorinating. effect is in factobtaine if any silver which may be resent as metal is firstconvertedinto' s'ul d. v

Accordingly myinvention consists in transforming the metallic silvercontent of such materials as contain the same into sulfid, as a stepprelimina to the formation and solution of silver c lorid For exam lo Imay treat'the leached residue or silni ar material containing metallicsilver with hydrogen sulfid or with an alkaline sulfid, or otherappropriate sulfidizing Specification of Letters Patent. Patented Mar.29, 1921;

' Application filed Hay 11, 1920. Serial No. 380,838.

agent, whereby the conversion occurs presumably according to thereaction;

This operation may be performed an approved way, such for, example asby'a tatmg the ore or residue in an aqueous so ution of hydrogen sulfidfor a sufiicient period,

' usually several hours, to convert the silver content to sulfid; thepulp being then filtered and washed. Or the ore 0r residue may becharged into vats with filter bottoms and a solution of hydrogen. sulfidthrough the mass, either by upward or downward percolation, for asufficient period to convert the silver to sulfid, the solution being.then withdrawn and the ore washed with water.

Or if preferred the moist ore or residue may be subjected in a revolvingcylinder to the action of air containing hydro en sulfid.

T e resulting sulfidized material is then treated with a suitablechloridizing a cut, as cu rous or cupric chlorid or chlorid: or mixturesthereof, preferably in presence of a solvent for silver chlorid. For thelatter urpose I may emplo solutions of sodium ch lorid or of other chorids having the desired solvent power. After separation of the silverbearing solution from theore, the silver is precipitated and recoveredin any well known way, as forexample by the] use of metallic copper. Anygold which may be present is s1multaneously recovered.

I claim 1. Method of extracting silver from ores or residues containingmeta lic silver, comprising converting the silver content of thematerial into sulfid, and chlorinating the sulfid.v j

2. Method according toclaim 1 in which the. sulfid is chlorinated 1'presence of a solvent for silver chlorid.

ERCY MIDD E In testimon whereof I allixm si am,

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